A series of dendritic multiporphyrin arrays (PZnTz-nPFB; n =2, 4, 8) comprising a triazole-bearing focal zinc porphyrin (PZn) with a different number of freebase porphyrin (PFB) wings has been synthesized, and their photoinduced energy transfer process has been evaluated. UV/vis absorption, emission, and time-resolved fluorescence measurements indicated that efficient excitation energy transfer takes place from the focal PZn to PFB wings in PZnTz-nPFB's. The triazole-bearing PZn effectively formed host-guest complexes with anionic species by means of axial coordination with the aid of multiple C-H hydrogen bonds. By addition of various anionic guests to PZnTz and PZnTz-nPFB's, strong bathochromic shifts of PZn absorption were observed, indicating the HOMO-LUMO gap (ΔEHOMO-LUMO) of PZn decreased by anion binding. Time-resolved fluorescence measurements revealed that the fluorescence emission predominantly takes place from PZn in PZnTz-nPFB's after the addition of CN-. This change was reversible because a treatment with a silver strip to remove CN fully recovered the original energy transfer process from the focal PZn to PFB wings.
Bibliographical noteFunding Information:
This work was supported by the Mid-Career Researcher Program (2014R1A2A1A10051083), Global Research Laboratory Program (2013K1A1A2A02050183) funded by the National Research Foundation (NRF) of Korea, Ministry of Science, ICT & Future, and the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (No. 20163030013960). The quantum calculations were performed using the supercomputing resources of the Korea Institute of Science and Technology Information (KISTI).
© 2016 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry